The objective of the research proposal is to study mechanisms of immunogenetics, autoimmunity and immunosuppression in order to translate experimental findings and concepts of basic and clinical immunology into knowledge which is useful for the diagnosis and treatment of human disease. New cell surface antigens coded for by the major histocompatibility complex (MHC) in man will be defined, and their association with specific rheumatic and autoimmune diseases will be studied. The immune response of HLA-B27 positive and negative individuals to purified antigens from strains of Shigella which do and do not cause Reiter's syndrome will be studied. Patterns of autoantibodies and clinical presentation will be investigated in the rheumatic diseases in order to further classify subtypes of disease. Finally, a new modality of immunosuppression, fractionated total lymphoid irradiation, will be studied for efficacy in the treatment of rheumatoid arthritis, autoimmune diseases of laboratory rodents, and rejection of allogeneic bone marrow transplants in dogs.